1. Field of the Invention
This invention relates to a fuel feed pump for internal combustion engines.
2. Background Art
Various types of feed pump are used as fuel supply pumps of vehicles. Conventionally, such pumps use a configuration that allows the maximum flow rate to be changed in order to make the pumps adaptable to a broad range of specifications. Japanese Public Disclosure No. Hei 8-210210, for example, discloses a feed pump used as the supply pump in a common-rail type fuel-injection pump. In the case of the disclosure, a pressure valve is provided in the bypass passage to make it possible to control the amount of fuel being moved. In accordance with this configuration, during normal operation a large quantity of fuel is fed to a high-pressure pump and fuel movement is suppressed at non-injection times. This makes it possible to prevent a large amount of fuel being wastefully circulated between the fuel pump and the fuel tank.
However, this conventional technology uses a check valve that is opened/closed in response to pressure, making it possible for contamination to occur by foreign matter being drawn onto the valve seat during valve operation, so that when the value is open the flow rate tends to be altered by the contamination. For this reason, control of the flow rate has not been very precise. Another problem has been that of the noise and vibration produced by the seating impact each time the valve opens and closes.